25.) How does ozone protect the earth’s surface from UV light? What are the reac

Question

25.) How does ozone protect the earth’s surface from UV light? What are the reactions?

26.) How does chlorine radical catalyze the destruction of ozone? What are the sources of chlorine into the stratosphere? What are freons? What properties of freons allow these molecules to travel into the stratosphere?

27.) What is meant by the “Antarctic Ozone Hole”? Polar Vortex? Polar Stratospheric Clouds? How do physical and chemical phenomena lead to the destruction of ozone in the Antarctic spring?

28.) What was done to alleviate the ozone-thinning problem? What effects will reductions in freon production have on stratospheric ozone?

Explanation / Answer

1) How does ozone protect the earth’s surface from UV light? What are the reactions?

The ozone protect the earth’s surface from UV light by absorbing most of the ultraviolet radiation before it reaches the earth's surface.

As both ozone and oxygen molecules are present in the earth's stratosphere and here they absorb UV light from the sun which help in providing a shield and this prevents these radiation from reaching the earth's surface.

They together absorb 95 to 99.9% of the sun's UV radiation and only ozone effectively absorbs the UV-C and UV-B which are most energetic UV light and causes biological damage.

When UV light reaches the earth stratosphere, it collides with one oxygen molecule (O2), and split into two oxygen atoms (2 O1).

The oxygen essentially absorbs the short-wavelength UV light.
O2 (oxygen gas) -> 2 O1 (atom)

The free oxygen atoms are unstable, and collide with other molecules of oxygen which form ozone (O3).
O1 (atom) + O2 (oxygen gas) -> O3 (ozone)

Short-wavelength UV light break apart ozone molecules. In this way, the ozone gas breaks into one oxygen gas molecule and an oxygen atom that absorbing much of the remaining UV light.
O3 (ozone) -> O1 (atom) + O2 (oxygen gas)

The O1 atom then combines with one O2 molecule to form O3 which absorb UV light.


2) How does chlorine radical catalyze the destruction of ozone? What are the sources of chlorine into the stratosphere? What are freons? What properties of freons allow these molecules to travel into the stratosphere?

A) Chlorine radical catalyze the destruction of ozone as follows:
Free chlorine (ClCl) in the stratosphere can deplete ozone (O3OX3) :
Cl+O3ClO+O2
Cl+OX3ClO+OX2

Then tge chlorine atoms react with oxygen, return to the beginning of the cycle again:
ClO+OCl+O2

B) Sources of chlorine:

As chlorine is unstable it is released in its elemental form and react with some other element or compound before it reach the stratosphere. However, chlorine is a key element of chlorofluorocarbons. Volcanoes are also source of chlorine as Volcanoes can add more chlorine into the stratosphere than CFC's.Sea salt add more chlorine into the atmosphere than CFC's

C) Chlorofluorocarbons or CFCs are known as Freon. They are non-toxic, non-flammable and non-carcinogenic and contain fluorine atoms, carbon atoms and chlorine atoms.

D) Because of their inert properties of freons they are used as ideal fire extinguishing, cleansing, and foaming agents, as solvents, and as aerosol propellants.

Low-pressure properties of freon makes them to vaporize easily and used as refrigerants.

Chemical inertness of freon makes them useful but also creates a problem, as they persist in the environment for long periods and diffusing into the stratosphere which decompose and then destruct the protective layer of ozone....

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